Transmission system



y 1934- D. THIERBACH 1,968,106

TRANSMISSION SYSTEM Filed Feb. 4, 1932 INVENTOR DIETWALD THIE'RBACH WWWATTORNEY Patented July 31, 1934 UNITED- sat-Ares I TRANSMISSION SYSTEMDietwald Thierbach Berlin-Spandau, Germany, assignorto Siemens & Halske,Aktiengesellschaft, Siemensstadt, near Berlin, Germany, a corporation.of Germany Application February 4-, 1932, Serial N0. 590,976

- Germany February 19., I931.

'7. enl sts; (or 25.0 m

The 'invention is concerned-with a. method: to control the: transmissionmeasure by the aid or a control frequency; and the same distinguishesitself from methods known the. prior artin that the control action isenacted by altering thefrequency of thecontrolling current.

In the operation of regeneration looks" or blocks it has been customaryin the prior art to block transmission in one directionin the presenceof the: control frequency, and to block transmission:

in the other direction upon the failure or absence of this controlfrequency. According to the meth- 0d of the present invention t'rafiicinone direction is blocked by one control frequency, and traffic in theother direction by another control frequency; Theconnection or switchingand rendering operative of. the various control frequenciesisinsured inthis scheme by the signal currents by art. 7 I

The inventionwill be found'particularIy ad vantageous if inaddition tothe regeneration block also a regulation of the volume level is to besecured. By the use of two comparatively adjacent frequencies it is:possible to effect: both these regulative actions. The volume regulator:and stabilizer means would in this case have to-be so designed that theywill respond to both: frequencies' Inasmuchas a control frequencyispresent all the time thismeans'thata continualregulation of volumelevel is insured. If the two frequencies are located close, enoughtogether, for example, say about. 100 cycles per second apart, thenfluctuations in the intensity of the: energy transmission over thedistance: covered,- say, by radio will affect both frequencies inlikemanner so that'a change of-the frequencyused for volume control andregulation will not-be at-- tended by any inconvenience The regenerationblocks should be so designed that they will be able to distinguishbetween or respond selectively tothe frequencies so that one or theother or the: two transmission paths will be opened or cleared dependingupon the frequency of the control-current, that is, which controlcurrent isoperative;

Designing the regeneration blocking means in such a manner that in thepresence of' both no: quencies of about like amplitude simultaneouslynochange in thesense' of" transmission is'produ'ced, this meansthat arather thorough insenways and means well-known in Y the sitiv'eness ofthe arrangement to disturbing o;

methods: known in. the prior art which utilize but one controlfrequency, do: notv offer this chance of obtaininga compensation ofatmospherics: or similar disturbances v The invention shall be explainedin. more detail by reference toa. practical; embodiment given. by way ofexample. The drawing showsa trans.- m-iss'ion: system. wherein. thecontrol frequencies used for the actuation of the regeneration. blocksare used atthe' same time for controlling or. stabilizing the level ofthe volume, Double conductors arev represented by single line,

The: merit residing. irrthe circuit scheme illustrated'. primarilyconsists in. that the operation of the blocking meansfor the twodirections are perfectly similar inasmuch as. a definite frequency is:provided. for: each direction of transmission. In. the. circuitarrangements heretofore. used; owing to the presence of the controlfrequency, one direction of traffic was blocked and the other onecleared; in other-words, the two blocks were actuated in contrarydirections.

1 The subscribers'T and T are united. by radio; S and E', respectively,denote the radio; transmitters and receivers; The receiving means areconnected with the regulating amplifiersRV whose transmission. measureor'amplification characteristic is regulated by the rectifiers G14. Therectifier-s: G14 respond to the: control frequencies.- transmitted';according to the invention. The-fil ter- K3 is broad: enough to passboth of the con.- trolling frequencies, which, as indicated above, areseparated by a relatively small difference frequency; as,. for example,100*- cycles per second,. whereas the filterKe. also connected with RVdoes: not. permit these frequencies to: reach the subscribersconnectionsr1, T. To actuate the. regeneration: blocks two'rectifiers G11 and G12:are connectedfby way of. the. filters K1 and K2 respectively to RV byway 'of'Ks, as shown. The reversing of the subscribers linesgjthat is,the changing from and to the transmitter and; receiver means,respectively, is effected by the agency of a relay R1 which is'providedwith twoopposed windings which are associated with the rectifiers. G1 1and G121 respectively. a

At the transmittingend there are two gener-. ator's GIand'G2 provided tosupply the control frequencies; 'The changing-over of the generators iseffected by way-of the keeper T2 of relay R32. This latter relay isunited with the subscribers' line by way of the rectifier G13.

In the state of inoperation' of the communication equipment in which therelays occupy positions as shown'in the drawing, the subscribers ofiicesare connected with the corresponding transmitter means;hence,'regeneration is not possible. The frequency furnished from thegenerator G2, in a way well-known in the art, serves for fadingregulation (compensation). This frequency is fed from the aerial to thereceiver E and from E through the regulating amplifier RV, through thefilter chain K3 and the rectifier G14 and back to RV to regulate thesame against fading.

The filter chains K1 and K2 are so dimensioned that the frequency of thegenerator G2 will be transmitted only by the filter chains K2. Throughthe intermediary of the rectifier G12 the action of this wave is so thatthe relay R1 holds its keeper in the position as illustrated. When thesubscriber T is sending out a communication the signal currents willcause the relay R2 to respond by Way of the rectifier G13. The generatorG2 is switched off, while the generator G1 is connected with thetransmitter. The frequency of the generator G1 is fed by way of thefilter K3 for the regulation or compensation of the fading effects tothe rectifier G14, and by i way of the filter chain K1 to the rectifierG11 which energizes one of the windings of the relay R1, so that thekeeper 1" is thrown over with the result that subscriber T is connectedwith the receiver E.

Now, if disturbing potentials happen to reach the receiver the risk offaulty operation of the regeneration block is very slight. For if thesedisturbing potentials happen to fall inside the region of the controlfrequency they will normally be contained in both frequencies toapproximately the same amplitude. The disturbing potentials will thusactuate both rectifiers G11 and G12. Since the currents furnished fromthe rectifiers are brought to act upon the relay R1 in opposite senses,these troublesome potentials will fail to release an action.

In case of a communication proceeding from the subscriber T to thesubscriber T, similar circuit changes will occur in the transmissionarrangement of the subscriber T and in the receiver arrangement of thesubscriber T.

Instead of using two generators for the production of the two controlfrequencies, it would be feasible also to employ but one generator towhich a condenser is connected in parallel for the object of insuringchanges in wave-length. The mechanical relays shown in the exemplifiedscheme of the drawing, as will be evident to the expert, could bereplaced also by thermionic tubes.

The application of the basic idea of this invention of using twofrequencies for the control of the transmission measure affords certainadvantages for the reasons as above set forth (atmosphericscompensation) if distinct level regulation is dispensed with or if thisis replaced by another regulation.

I claim:

1. A duplex signalling system, each end of which includes a transmittingmeans, receiving means, a subscribers line, a first switch connectedthereto, a plurality of control frequency generators at eachtransmitter, switching means for alternately connecting said controlfrequency generators to said transmitter, a balanced relay at eachreceiver, said relay being opcratively related to said first switch, acontact adjacent said first switch connected to said transmitter, saidcontact being normally closed, a contact adjacent said first switchconnected to said receiver, said contact being normally open, and filtermeans interposed between said receiver and said relay whereby when onecontrol frequency is transmitted said subscribers line is connected bysaid first switch to said transmitter, and when another controlfrequency is transmitted said subscribers line is switched to saidreceiver.

2 An arrangement as claimed in claim 1 in which said control frequencygenerators operate at different frequencies and in which the position ofsaid switching means for alternately connecting said control frequencygenerators determines which control frequency generator is connected tosaid transmitter.

3. A duplexing system comprising, two or more stations, each including atransmitter and a subscribers line, a pair of control frequencygenerators, switching means normally connecting one of said controlfrequency generators to said transmitter, a second switching meansnormally connecting said subscribers line to said transmitter, a relayassociated with said first named.

receiver at each of said stations disconnected from said subscribersline, each of said receivingmeans also including a second filterconnected with said receiver and with said relay andresponsive to thefrequency transmitted when said other control frequency generator isconnected with said transmitter of said other station to energize saidrelays to move said second switch in a position to connect said receiverto said subscribers line when signal frequencies are im- 1 pressed fromthe subscribers line at the. other station on the transmitter.

4;. A duplexing system as claimed in claim,3 in which each of saidreceivers includes automatic volume control means actuated by either ofsaid control frequencies. I

5. A duplexing system as recited in claim 3 in which said controlfrequency generators generate frequencies separated by a narrow band offrequencies, and in which said receivers each in clude a filter tunedbroad enough to pass the frequencies of both of said control frequencygenerators, and automatic volume control means connected with saidfilter and with said receivers.

6. A duplexing system comprising stations in cluding, a transmitter anda receiver, a sub-- scribers line normally connected with saidtransmitter, a pair of oscillation generators generating frequencieswhich differ by approximately- 100 cycles per second, a relay in saidreceiver responsive to one of said control frequencies for maintainingsaid transmitter normally connected to said subscribers line, and meansin said relay responsive to the other of said control frequenl1 cies fordisconnecting said transmitter from said subscribers line and connectingsaid receiver to said subscribers'line."

7. A duplexing system as recited in claim in which each of saidreceivers includes an automatic volume control means responsivev toeither of said control frequencies.

DIETWALD THIERBACH.

